Why are your DSL prices higher than some competitors?
Check out the fine print on the competitors' web pages. Chances are their services are metered, meaning that you are only allowed so much traffic before they hit you with an additional usage charge. And those added charges are not cheap!
Also those competitors' emphasize that they only meter the "upload" usage, but that usage can soar if you are using certain interactive and realtime services such as streaming video or music simply because your computer has to talk to the server all the time.